[Xen-devel] [PATCH for-4.12 3/8] iommu/pvh: add reserved regions below 1MB to the iommu page tables

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Reserved memory ranges below 1MB on a PVH dom0 are added to the HAP
page tables, but due to this being done before setting up the IOMMU
the non RAM regions in those areas are not added to the IOMMU page
tables. Fix this by making sure any reserved regions below 1MB are
added to the IOMMU page tables.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
---
Without this patch creating a PVH dom0 can cause iommu page faults and
non-functional devices.
---
 xen/drivers/passthrough/x86/iommu.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/xen/drivers/passthrough/x86/iommu.c 
b/xen/drivers/passthrough/x86/iommu.c
index a88ef9b189..d3639d1538 100644
--- a/xen/drivers/passthrough/x86/iommu.c
+++ b/xen/drivers/passthrough/x86/iommu.c
@@ -151,12 +151,7 @@ static bool __hwdom_init hwdom_iommu_map(const struct 
domain *d,
      * inclusive mapping additionally maps in every pfn up to 4GB except those
      * that fall in unusable ranges for PV Dom0.
      */
-    if ( (pfn > max_pfn && !mfn_valid(mfn)) || xen_in_range(pfn) ||
-         /*
-          * Ignore any address below 1MB, that's already identity mapped by the
-          * Dom0 builder for HVM.
-          */
-         (!d->domain_id && is_hvm_domain(d) && pfn < PFN_DOWN(MB(1))) )
+    if ( (pfn > max_pfn && !mfn_valid(mfn)) || xen_in_range(pfn) )
         return false;
 
     switch ( type = page_get_ram_type(mfn) )
@@ -245,7 +240,12 @@ void __hwdom_init arch_iommu_hwdom_init(struct domain *d)
         if ( !hwdom_iommu_map(d, pfn, max_pfn) )
             continue;
 
-        if ( paging_mode_translate(d) )
+        /*
+         * Don't add any address below 1MB to the HAP page tables, that's
+         * already done by the domain builder. Add addresses below 1MB to the
+         * IOMMU page tables only.
+         */
+        if ( paging_mode_translate(d) && pfn >= PFN_DOWN(MB(1)) )
             rc = set_identity_p2m_entry(d, pfn, p2m_access_rw, 0);
         else
             rc = iommu_map(d, _dfn(pfn), _mfn(pfn), PAGE_ORDER_4K,
-- 
2.20.1


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